first, don't sell yourself short--orgasms
are a big deal. yes, sex can be pleasurable without them--but they are important. when i first started having sex, i thought, well, it's ok if i don't have an orgasm every time. which eventually translated into--he got one every time and i got one...well, virtually never. so then i had to train both my partner
and myself to recognize that orgasms are an important part of sex. and sex became much more enjoyable after--i don't have to have a big one every time, but there does have to be some level of climax to the experience. the more often you get them, the more often you want them--that works in reverse too. when i wasn't getting them, sex was ok but the level of pleasure wasn't as intense--and that lowered expectation made it more difficult to really get into it so that i could climax. make sense? it goes with what the gyno with great advice said--the more you have, the more you will have!
there's tons of great advice in this thread regarding getting there, but have you ever orgasmed with a partner? i realize not during sex--but you know your body is capable if your doing it while masturbating, so what about when he stimulates your clit? to me, "letting go" is tied to comfort levels, both with yourself and with your partner. since you orgasm when masturbating, sounds like you are relatively comfy with yourself. try having him get you off using the same methods you use yourself. if it happens, then most likely it's not inhibitions stopping you but just finding the best way to stimulate you. if you can't orgasm that way, then perhaps you need to work on opening yourself up with your partner so that you are comfy just letting go and enjoying the ride